What Could Cause Sudden Redness, Pain, And Swelling In The Tip Joint Of My Finger Without Injury Or Arthritis?

My right third finger started hurting at the farthest out joint early afternoon today. Quite red and painful. It hurts to bend and has sort of a throbbing ache. I just took an ibuprofen and am going to use ice and a popsicle stick to restrict movement. I m healthy, don t have arthritis, lupus, etc. I don t see any sign of a bite. I ve used it on the keyboard, not excessively, and put a ring over that finger earlier. Not tight. Any suggestions?